Is anyone using a transformer to bump 240v to 460v through a RPC? Thanks
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Transformer and a RPC
- Thread starter 930dreamer
- Start date
malibu101
Well-known member
I don't understand. What are you trying to do?
A simple transformer will take 240 to 460.
An RPC is to "make" 3 phase power from single phase.
You're kinda asking 2 different things.
A simple transformer will take 240 to 460.
An RPC is to "make" 3 phase power from single phase.
You're kinda asking 2 different things.
OP
I don't understand. What are you trying to do?
A simple transformer will take 240 to 460.
An RPC is to "make" 3 phase power from single phase.
You're kinda asking 2 different things.
I have a 10 hp & 7.5 hp=17.5 hp rpc combo currently running. I want to add a 3 phase transformer off the combo and bump everything downstream to 460v to cut my amps. I'll then add three more idlers and use 460v.
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hillbilly1
Well-known member
- Joined
- Sep 16, 2010
- Messages
- 99
Cutting your amps by doubling the voltage will not reduce your load, about all the good it will do is if you have a voltage drop problem with long runs of wire.
OP
Cutting your amps by doubling the voltage will not reduce your load, about all the good it will do is if you have a voltage drop problem with long runs of wire.
If I wire my 3 phase motors to the higher voltage I'll cut the load amps in half.
If I wire my 3 phase motors to the higher voltage I'll cut the load amps in half.
For what reason do you want to cut your load amps in half? What is the up side here that you hope to gain?
lg
no neat sig line
OP
For what reason do you want to cut your load amps in half? What is the up side here that you hope to gain?
lg
no neat sig line
I want to start a 30 hp RPC idler to see if I can start a 15 hp compressor. I may need to upgrade the panel.
The primary reason home shop folks use a transformer & RPC is when a motor is rated for 440 or 460V only, & rewinding or replacing it is not feasible, just going to 480V is not going to help you, there will still be the higher current on the transformer primary & 480 volts is not for untrained/unqualified people. The same applies to 550,575V motors on a 600V system.
just going to 480V is not going to help you, there will still be the higher current on the transformer primary & .
Norcal you said what I was leading up to. Shifting up your voltage is still going to draw the same POWER from the 240 single phase that you are starting with, as well as the losses through the transformers. Now if like Norcal said you only have a 480v capable motor on the compressor then you will have to transform the voltage. If your thinking that transforming up the voltage will get more power to kick over the 15hp compressor I believe you will be disappointed. Rough swag is that your going to have to have a better than 50A supply to this system.
lg
no neat sig line
malibu101
Well-known member
What you are about is POWER also know as WATTS.
P= watts
E= volts
I= amps
R= resistance
Our good old laws tell us that------
E x I = P
P / I = E
What you suggest will only add more load (due to the transformer loss) costing you more watts. I don't see how you'll gain anything. But I may be wrong.
P= watts
E= volts
I= amps
R= resistance
Our good old laws tell us that------
E x I = P
P / I = E
What you suggest will only add more load (due to the transformer loss) costing you more watts. I don't see how you'll gain anything. But I may be wrong.
OP
Do I have any options, my main concern is amps because of the load center limits. No electric bill with my shop lease. I want to test two 15 hp Champion compressors so motor change isn't an option. Thanks for all the help, Shawn.
I use a step-up transformer (actually just a regular transformer wired backwards) to change the 220V 3-phase out of my RPC to 460V. I run both my lathe and mill on 460V.
Primary reason for this was that the lathe has a two speed motor and can only run on 460V. I only paid $70 for the 45kVA transformer, so it was the obvious choice vs. trying to find a 220V two speed motor for it. Replacing it with a single speed motor was not an option as I'd lose half the spindle speeds, and it's pretty lacking as it is (30-1200 rpm).
Primary reason for this was that the lathe has a two speed motor and can only run on 460V. I only paid $70 for the 45kVA transformer, so it was the obvious choice vs. trying to find a 220V two speed motor for it. Replacing it with a single speed motor was not an option as I'd lose half the spindle speeds, and it's pretty lacking as it is (30-1200 rpm).
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Do I have any options, my main concern is amps because of the load center limits. No electric bill with my shop lease. I want to test two 15 hp Champion compressors so motor change isn't an option. Thanks for all the help, Shawn.
your amps on the 240v side will be the same as if you were using a 240v motor. the amps will only be lower on the 460v side of the transformer. how is this going to help with your loadcenter?
hidollartoys
Well-known member
You are going to be about 30hp short on the RPC to start a 15hp compressor under load. Per the RPC mfg'rs that I have talked to, you need about 4 times the hp relative to the compressor motor. This becomes increasingly critical at higher HPs.
OP
your amps on the 240v side will be the same as if you were using a 240v motor. the amps will only be lower on the 460v side of the transformer. how is this going to help with your loadcenter?
I have no issues starting my 10/7.5 rpc combo on a 50 amp circuit. I can cut the amps in half after the transformer and start the other idlers, 7.5/10/15 hp. If I got this far I'd try and start the 30 hp idler.
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OP
oh, so youll put additional idlers after the transformer? what are you going to use to switch them, for overcurrent protection, etc? 480v is a whole different game...
No expert here, disconnect?
No expert here, disconnect?
ok, say you have your transformer, how are you going to connect everything on the 480v side?
OP
ok, say you have your transformer, how are you going to connect everything on the 480v side?
Run each motor in parallel through disconnects.